1. Field of the invention
The present invention relates to a surgical microscope and more particularly to a light source apparatus for surgical microscopes.
2. Description of the prior art
Recently, what is called microsurgery in which a delicate surgical operation is performed while a part to be operated upon is magnified and observed under a microscope, has been largely adopted. According to the microsurgery, from the fact that a delicate surgical operation is performed with accuracy, many favorable results have been achieved not only in ophthalmology, cerebral nerve surgery and otorhinology but also in various fields. Also in such microsurgery, it is necessary to photograph a part to be operated and an operating technique for education and study, as in other operations, and magnification photographing relying on a surgical microscope often brings about inevitably the lack of a sufficient amount of light. As a result, an Xe flash lamp (stroboscopic lamp) is used as an auxiliary light source for photographing and, in the past, various stroboscopic devices for surgical microscopes have been designed. Of these devices, the commonest one has a system that the Xe flash lamp is attached adjacent to a tube of the surgical microscope as illustrated in FIG. 1. That is to say, in FIG. 1, reference numeral 1 represents an objective tube section of the surgical microscope, in which an illuminating optical system for observation, an observing optical system and driving devices for these systems, not shown, are incorporated. Then, a light beam, incident on the objective tube 1, coming from a part to be operated is divided by a beam splitter, not shown, incorporated likewise in the objective tube 1 and an operation is performed in a such state that the one of the light beam travels to a photographing device 4 for photographing, while the other travels to an eyepiece 2 to be observed with an operator's eye 3. Reference numeral 7 indicated in broken lines represents, in an illustrating manner, an eye to be operated. For such an operation of the eye in ophthalmology, an illuminating device 5 including an optical axis B intersecting obliquely with an optical axis A of an objective lens 9 is mounted to the objective tube 1. The illuminating device 5 for illuminating the part to be operated has an Xe flash tube 5a as a light source for illumination and a lens 5b for condensing light emitted from the Xe flash tube 5a at the part to be operated.
In such an illuminating device 5 arranged obliquely in respect of the optical axis A, there has been a defect that, when an affected part to be operated which is narrow and deep in aperture, like an affected part 8a to be operated in otorhinology and cerebral nerve surgery shown in solid lines, is illuminated, illuminating light cannot completely reach the affected part 8a due to its oblique illumination and an illuminating effect is not brought about. To solve this problem, in the past, a method has been adopted that a direct suspension type illuminating device 6 is attached to the objective tube 1 in close vicinity to the objective lens 9 and the affected part 8a is illuminated, through the aperture of a cranium 8, by an Xe tube 6a placed in the direct suspension type illuminating device 6 and an objective lens 6b for illumination to condense light from the Xe tube 6a at the affected part. Also in the use of the direct suspension type illuminating device 6, however, it is necessary to extend its illuminating section in the vicinity of the optical axis A of the objective lens 9 and, as a result, a visual field for observing directly the part to be operated with the operator's naked eye has been obstructed. Further, it is limited to set the illuminating section near the optical axis A and, in fact, even the direct suspension type illuminating device 6 emits somewhat obliquely the illuminating light, with the result that the affected part 8a with a deep region is inevitably subjected to uneven illumination. Because the oblique illuminating device or the direct suspension type illuminating device is attached, in either case, to the outside of the objective tube 1 as mentioned above, a space necessary for an operator in the surgical operation would be blocked. Originally, a microscope for an assistant and other apparatus for operation are provided in the objective tube 1 of the surgical microscope, so that the operating space is made narrow, further by mounting the illuminating device for photographing, and the operator's operation would be disturbed.
In order to solve the above-mentioned problem, such a device as shown in FIG. 2 is thus disclosed in Japanese Utility Model Preliminary Publication No. Sho 60-31691, for example. That is to say, a microscopic tube 12 is coupled to a microscopic base arm (not shown) by a support arm 11. In the tube 12, a replaceable objective lens 22 is provided to change a focal distance depending on an operating manner or the depth of the affected part to be operated. Further, in the tube 12 is incorporated a light guide 18 comprising an optical fiber for supplying illuminating light for observation which continues to illuminate the affected part to be operated during the surgical operation and the illuminating light emitted from the light guide 18 is condensed by the objective lens 22 to illuminate the affected part. Reflecting light coming from the affected part to be operated traverses again the objective lens 22 and after passing through a magnification optical system 19 of a Galileo type binocular microscope optical system, is incident on a beam splitter 14. The light incident on the beam splitter 14 is reflected by a half transmitting surface 14b, is further reflected by a reflecting surface 14a and then is formed as an image on a film 13b through an image forming lens 13a of a photographing device 13 for photographing. On the other hand, light transmitting the half transmitting surface 14b of the beam splitter 14 is reflected from a reflecting surface 14c, is further reflected from a reflecting surface 15a of a reflecting optical member 15 of an eyepiece section and is last reflected by a reflecting surface 16a of another reflecting optical member 16 so as to enable the operator to observe the affected part to be operated through an eyepiece system 17. Also, the tube 12 incorporates an illuminating device 21 for photographing in a space between a driving device 20 of the magnification optical system 19 the objective lens 22. The illuminating device 21 for photographing comprises a socket 21a and a lamp house 21c which has an Xe lamp 21d and which is coupled to the socket 21a by a plug 21b and electric power for trigger and electric power for illumination are supplied from the socket 21a through the plug 21b. A shading plate 23 is interposed between the illuminating device 21 for photographing and the magnification optical system 19 so that light is not incident on the magnification optical system 19 from the Xe lamp 21d.
Also, in a retinal camera, it is a known system that the Xe lamp is arranged at a position optically conjugate with a light source for observation in an illuminating optical system for observation so that an illuminating optical axis for observation may coincide with an illuminating optical axis for photographing. In other words, as shown in FIG. 3, the system is such that a filament image of a light source lamp 34 for observation is formed at the center of an Xe lamp 33 through an illuminating optical system 36a and a field of operation is illuminated by an illuminating optical system 36b and an objective lens 32. Also, reference numeral 31 denotes a microscopic tube and 35 a magnification optical system.
In the device described in Japanese Utility Model Preliminary Publication No. Sho 60-31691, however, what is used as a measure for condensing a light beam from the Xe lamp 21d is only the objective lens 22. In addition, since the light beam emitted from the Xe lamp 21d is diverged and the focal distance of the objective lens 22 is 150-300 mm, whereas the Xe lamp 21d is placed at a distance of several tens of millimeters from the objective lens 22, its illuminating field is much widely enlarged as compared with a photographing region and consequently the amount of light reaching the photographing region is nothing but several percents of the total amount of light obtained from the Xe lamp 21d. Further, the illuminating field is more largely covered with the reduction of illumination as the focal distance of the objective lens 22 becomes longer and, at the same time, the numerical aperture of the observing optical system is reduced as the focal distance of the objective lens 22 becomes larger, so that the amount of light reaching a film surface becomes extremely small when the focal distance of the objective lens 22 is long. Since it is therefore required that the Xe lamp 21d has light-emitting energy of several hundreds of joules to secure the amount of light sufficient for photographing, there has been a problem that both the Xe lamp 21d and the light source section are inevitably used in large size and, as a result, the body of the microscope housing the Xe lamp 21d is also increased in size. Also, if the luminous intensity of the Xe lamp 21d is automatically controlled for the simplification of photographing, electric power to be supplied into the Xe lamp 21d becomes very high. In addition, with the surgical microscope, the distance between the objective lens and the affected part to be operated is widely different depending on a region to be operated and magnification for observation needs to be largely changed in accordance with the purpose of operation, so that the control of the luminous intensity with very high degree of accuracy is required, and there has been a problem that such a control circuit is substantially difficult to be realized. Furthermore, there is an indication of a problem that, since the optical axis of the Xe lamp is different from that of the illuminating light for observation, when the operation of a deep region is performed through a narrow aperture, the illuminating light for observation reaches the affected part to be operated, while on the other hand, the light of the lamp cannot pass through the aperture and therefore it may be impossible to take a photograph.
Also, in the device shown in FIG. 3, the optical axes of the illuminating light for observation and the light of the Xe lamp are arranged to be completely coaxial and the light from the Xe lamp 33 is condensed through the illuminating optical system 36b, with the result that the efficiency of the light intensity of the Xe lamp is markedly improved as compared with the device described in Japanese Utility Model Preliminary Publication No. Sho 60-31691. However, a problem has been encountered that, when the light beam of the light source lamp 34 passes through the Xe lamp 33, the amount of light is lost due to the surface reflection of the lamp 33 and a common amount of light for observation will be lacking.
Thus, as shown in FIG. 4, it has been devised that a free directional light deflecting device is arranged in the illuminating optical system for observation so that an optical system provided in the rear of the light deflecting device of the illuminating optical system for observation is used in common with the illuminating optical system for photographing and that the arrangement is made so that only one of both the illuminating optical systems is selected by the switching of the light deflecting device, the light from a light source for photographing is once converged, the optical axis of the illuminating light for observation completely coincides with that of the illuminating light for photographing and the light from the illuminating light source for observation is not blocked by that from the illuminating light source for photographing. That is, in FIG. 4, reference numeral 43 represents an Xe flash lamp, 44 a relay lens system, 45 a light source lamp, 46 a relay lens system, and 47 a leaping-up mirror provided to select either illuminating system relying on the light source lamp 45 or the Xe flash lamp 43. When the arrangement is made as mentioned above, the illuminating device for photographing securing a large amount of light can be constructed by means of the Xe flash lamp with low electric power which is substantially the same as a stroboscopic lamp for ordinary cameras, without the loss of the amount of light of the illuminating device for observation, and as such a small-sized and power-saving surgical microscope is available. Moreover, the illuminating light for observation is completely in a coaxial relation with respect to the illuminating light for photographing, so that it is possible to be photographed even in the surgical operation performed through a narrow aperture. Also, the electric power may be low even when the light intensity of the illuminating device for photographing is automatically controlled, and therefore the surgical microscope, which can employ a small-sized light intensity controlling device, can be materialized with ease and at a low cost. When the optical system is arranged as stated above, however, there has been a serious danger that since the leaping-up mirror 47 interlocks with the shutter of a camera to leap to a position 47' indicated in broken lines followed by the emission of light from the Xe flash lamp 43, the illuminating light is interrupted for a few seconds and, as a result, not only uneasiness is caused in the surgical operator's mind, but also operating time may be prolonged.